The overall purpose of this project is to extend a series of highly successful experiments testing the hypothesis that the reflexive startle response is modulated by emotional state. The new experiments will critically examine the biphasic model of emotion. In this view, emotions are motivationally driven by reciprocal brain states, either appetitive (favoring approach, attachment, and consummatory behavior) or aversive (favoring avoidance, escape, and defense). Furthermore, the response system as a whole (from cognitions to exteroceptive reflexes) is tuned according to the current status of this central affect-motivational organization. Thus, reflexes associated with an appetitive set should be enhanced, if activated when the subject is already engaged in a positive emotional response; conversely, the startle reflex to a sudden noise is an aversive, defensive response, and would be augmented if it occurred in the context of an ongoing aversive emotion. Inhibition of startle in an appetitive context is also postulated. Specific experiments testing this view manipulate parameters of probe startle stimuli, and examine variations in emotional foregrounds and subject populations. The research is intended to determine: (1) if reflex modulation occurs for both visual and auditory startle probes, in both pictorial and auditory emotional foregrounds; (2) if these effects are in any way constrained by probe intensity or aversiveness; and, further, this work will (3) pursue the significance of lateralized probes for theories of the hemispheric processing of emotion; and (4) begin to determine if the affect-startle effect is unique to startle probes, or is a general phenomena of defensive reflexes. The research will manipulate characteristics of the emotional foregrounds tested by the probe methodology: to determine (1) if the affect-startle effect is consistent at different intensities of foreground emotion and (2) if reflex augmentation is consistent across different negatively valent emotional states; and, further, (3) to explore the effect during emotional memory imagery; and (4) to begin an examination of individual temperament differences in emotional state modulation of the startle reflex.